Method for use in making a write coil of magnetic head

ABSTRACT

Methods suitable for use in making a write coil of a magnetic head includes the steps of forming a seed layer made of ruthenium (Ru) over a substrate; forming, over the seed layer, a patterned resist having a plurality of write coil trenches patterned therein; electroplating electrically conductive materials within the plurality of write coil trenches to thereby form a plurality of write coil layers; removing the patterned resist; and performing a reactive ion etch (RIE) in ozone gas (O 3 ) for removing exposed seed layer materials in between the plurality of write coil layers. Advantageously, the write coil layers remain undamaged from the RIE in the ozone gas. Other structures may be fabricated in a similar manner.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to magnetic heads in disk drives, andmore particularly to improved methods of making write coils of magneticwrite heads as well as other structures with use of a ruthenium (Ru)seed layer for electroplating and a reactive ion etch (RIE) in ozone gasfor seed removal.

2. Description of the Related Art

A write head is typically combined with a magnetoresistive (MR) readhead to form a merged MR head, certain elements of which are exposed atan air bearing surface (ABS). The write head comprises first and secondpole pieces connected at a back gap that is recessed from the ABS. Thefirst and second pole pieces have first and second pole tips,respectively, which terminate at the ABS. An insulation stack, whichcomprises a plurality of insulation layers, is sandwiched between thefirst and second pole pieces, and a coil layer is embedded in theinsulation stack. A processing circuit is connected to the coil layerfor conducting write current through the coil layer which, in turn,induces write fields in the first and second pole pieces. A non-magneticgap layer is sandwiched between the first and second pole tips. Writefields of the first and second pole tips at the ABS fringe across thegap layer. In a magnetic disk drive, a magnetic disk is rotated adjacentto, and a short distance (fly height) from, the ABS so that the writefields magnetize the disk along circular tracks. The written circulartracks then contain information in the form of magnetized segments withfields detectable by the MR read head.

It is important to reduce the size of various structures within themagnetic head to achieve higher bit densities. One component ofimportance is the write coil, where the distance between each write coillayer (i.e. the “pitch”) has been reduced to 0.5 microns or less.

One conventional method of fabricating the write coil utilizesthrough-mask-plating (TMP), which is described in relation to FIGS.10–11. In FIG. 10, a seed layer 1004 is deposited over a substrate and aplurality of write coil layers 1002 are formed over seed layer 1004.Seed layer 1004 is typically made of materials such as copper (Cu) orgold (Au). Write coil layers 1002 are typically copper (Cu) materialswhich have been electroplated with use of a patterned resist. For highaspect ratio structures, a problem arises when seed layer 1004 betweeneach coil layer 1002 needs to be removed after the electroplating step.

One approach to remove seed layer 1004 between each coil layer 1002 isby ion milling, the result of which is shown in FIG. 11. After the ionmilling, seed layer materials 1104 may not be fully removed and topportions of write coils 1102 may be damaged. Write coils 1102 may becomeelectrically shorted. Note that it is difficult to etch the seedmaterials from the top of the structure in this manner, as the coillayers are relatively tall and the pitch between coil layers is narrow.With sputter etching (SE), the seed layer to be etched is immersed in aglow discharge where ions are accelerated across a sheath. Since theaccelerated ions are not collimated, the process requires over-etchingof the seed materials. The drawback to this approach is the increaseddepletion of the write coil thickness, which requires increasing theplating thickness of the write coils. Ion beam etching (IBE) is expectedto have a tighter collimation of accelerated ions from a set of gridsused to bias ions generated from confined plasma. Having a moreefficient seed removal process, the IBE requires less over-etching ofthe seed materials. However, both SE and IBE approaches still have anumber of shortcomings as the pitches are reduced. Namely, since theejected species in both approaches are not inherently volatile,redeposition can occur and cause an electrical shorting of the writecoils. Thus, since both techniques use purely physical processes toremove the seed materials, their selectivity is generally poor andover-etching tends to cause damage to the top coil structure and changethe topography to the extent that it introduces more complicationsduring subsequent fabrication steps.

Another conventional method of fabricating the write coil utilizes adamascene technique, which is described in relation to FIGS. 12–15. InFIG. 12, a dielectric structure 1202 such as a patterned resist isformed with a plurality of trenches. In FIG. 13, a thin seed layer 1302is deposited over the entire dielectric structure 1202 including withinthe trenches. Damascene electroplating of copper (Cu) 1402 is thenperformed within the trenches and over dielectric structure 1202 in FIG.14 to form a plurality of write coil layers. Next, a planarizationprocess such as a chemical-mechanical polishing (CMP) is performed overthe structure to remove top excess portions of the copper, to result ina write coil structure 1502 of FIG. 15.

This damascene technique of FIGS. 12–15 is useful in many situations.When the write coil's aspect ratio increases (i.e. the pitch betweencoil layers is reduced), however, the damascene technique has itslimitations. For example, fabrication issues become more apparent whenthe pitch between coil layers is 0.5 microns or less. For one, the seedlayer deposition becomes non-uniform. In addition, the damascene fillingwithin the trenches is also non-uniform and voids (e.g. a void 1504 inFIGS. 14–15) remain within the structure after the electroplating.Furthermore, the damascene technique for such high aspect ratiostructures is limited to metals which do not produce hydrogen evolutionduring electroplating; thus the technique is not applicable to magneticmaterials which are used to form other structures within a magnetichead.

Accordingly, there is a resulting need for a method of fabricating writecoils and other structures so as to overcome the deficiencies of theprior art.

SUMMARY

Methods suitable for use in making a write coil of a magnetic headincludes the steps of forming a seed layer made of ruthenium (Ru) over asubstrate; forming, over the seed layer, a patterned resist having aplurality of write coil trenches patterned therein; electroplatingelectrically conductive materials within the plurality of write coiltrenches to thereby form a plurality of write coil layers; removing thepatterned resist; and performing a reactive ion etch (RIE) in ozone gasfor removing exposed seed layer materials in between the plurality ofwrite coil layers. Advantageously, the write coil layers remainundamaged from the RIE in ozone gas.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings:

FIG. 1 is a planar view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane II—II;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is a partial elevation view of the slider and magnetic head asseen in plane V—V of FIG. 2, where the magnetic head includes amagnetoresistive (MR) read sensor and a non-pedestal type write head;

FIG. 6 is a top view of the second pole piece and coil layer, a portionof which is shown in FIG. 5, with all insulation material removed;

FIG. 7 is a partial ABS view of the slider taken along plane VII—VII ofFIG. 5 to show the read and write elements of the magnetic head;

FIG. 8 is a partial elevation view of the slider and magnetic head asseen in plane V—V of FIG. 2, where the magnetic head includes an MR orgiant magnetoresistive (GMR) read sensor and a pedestal-type write head;

FIG. 9 is a partial ABS view of the slider taken along plane IX—IX ofFIG. 8 to show the read and write elements of the magnetic head of FIG.8;

FIGS. 10–11 are illustrations pertaining to a conventional method ofmaking a write coil of a magnetic head with use of electroplating andion milling;

FIGS. 12–15 are illustrations pertaining to another conventional methodof making a write coil of a magnetic head based on a damascene techniquewhere a pitch between write coil layers is 0.5 microns or less;

FIG. 16 is a flowchart for use in describing a method of making a writecoil of a magnetic head in a disk drive (e.g. FIGS. 1–9) in accordancewith the present application; and

FIGS. 17–22 are cross-sectional views of partially constructed magneticheads for use in describing the steps in the flowchart of FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The methods described herein are suitable for fabricating a write coilof a magnetic head where a pitch between coil layers is 0.5 microns orless. The method includes the steps of forming a seed layer made ofruthenium (Ru) over a substrate; forming, over the seed layer, apatterned resist having a plurality of write coil trenches patternedtherein; electroplating electrically conductive materials within theplurality of write coil trenches to thereby form a plurality of writecoil layers; removing the patterned resist; and performing a reactiveion etch (RIE) in ozone gas for removing exposed seed pluralitymaterials in between the plurality of write coil layers. Advantageously,the plurality of write coil layers remain unetched from the RIE in ozonegas. Other structures may be fabricated in a similar manner.

The following description is the best embodiment presently contemplatedfor carrying out the present invention. This description is made for thepurpose of illustrating the general principles of the present inventionand is not meant to limit the inventive concepts claimed herein.

Referring now to the drawings, wherein like reference numerals designatelike or similar parts throughout the several views, there is illustratedin FIGS. 1–3 a conventional magnetic disk drive 30. Disk drive 30includes a spindle 32 that supports and rotates a magnetic disk 34.Spindle 32 is rotated by a motor 36 that, in turn, is controlled by amotor controller 38. A horizontal combined magnetic head 40 for readingand recording is mounted on a slider 42. The methods of the presentapplication may be utilized to make one or more structures (e.g. a writecoil) within magnetic head 40. Slider 42 is supported by a suspension 44and actuator arm 46. A plurality of disks, sliders and suspensions maybe employed in a large capacity direct access storage device (DASD), asshown in FIG. 3. Suspension 44 and actuator arm 46 position slider 42 tolocate magnetic head 40 in a transducing relationship with a surface ofmagnetic disk 34. When disk 34 is rotated by motor 36, slider 42 issupported on a thin (typically, 0.05 μm) cushion of air (air bearing)between the disk and an air bearing surface (ABS) 48.

Magnetic head 40 may be employed for writing information to multiplecircular tracks on the surface of disk 34, as well as for readinginformation therefrom. Processing circuitry 50 exchanges signalsrepresenting such information with magnetic head 40, provides motordrive signals, and also provides control signals for moving slider 42 tovarious tracks. In FIGS. 1 and 4, slider 42 is shown mounted to a headgimbal assembly (HGA) 52 that is mounted to suspension 44. All of theabove components are supported on a base 53.

FIG. 5 is a side cross-sectional elevation view of a conventional mergedmagnetoresistive (MR) head 40 as viewed in plane V—V of FIG. 2. Magnetichead 40 has a write head portion 54 (“non-pedestal type”) and a readhead portion 56. The read head portion includes an MR sensor 58. MRsensor 58 is sandwiched between first and second gap layers 60 and 62that are, in turn, sandwiched between first and second shield layers 64and 66. In response to external magnetic fields, the resistance of MRsensor 58 changes. A sense current conducted through MR sensor 58 causesthese resistance changes to be manifested as potential changes, whichare processed by the processing circuitry 50 shown in FIG. 3.

Write head portion 54 of the head includes a coil layer 68 sandwichedbetween first and second insulation layers 70 and 72. First and secondinsulation layers 70 and 72 are referred to as an “insulation stack”.Coil layer 68 and first and second insulation layers 70 and 72 aresandwiched between first and second pole pieces 76 and 78. First andsecond pole pieces 76 and 78 are magnetically coupled at a back gap 80,and have first and second pole tips 82 and 84 that are separated by anon-magnetic gap layer 86 at the ABS. Note that coil layer 68 iscontained completely above non-magnetic gap layer 86 under and withinsecond pole piece 78. As shown in FIGS. 2 and 4, first and second solderconnections 88 and 90 connect leads (not shown) from MR sensor 58 toleads 96 and 98 on suspension 44; third and fourth solder connections100 and 102 connect leads 104 and 106 from write coil 68 (see FIG. 6) toleads 108 and 110 on suspension 44.

FIG. 8 is a partial cross-sectional view of another conventional sliderand magnetic head (“pedestal type”) as viewed in plane V—V of FIG. 2,where the magnetic head may include an MR or a GMR sensor. FIG. 9 is apartial ABS view of the slider taken along plane IX—IX of FIG. 8 to showread and write elements of this magnetic head. Although many componentsin this magnetic head are the same as those in FIG. 5, some differencesare apparent. For one, the head in FIG. 8 includes a pedestal-type writehead wherein first pole piece 76 includes a first pole piece layer 80and a plated pedestal 152. Pedestal 152 is formed on first pole piecelayer 80 by electroplating and is made of a magnetic material having ahigh magnetic moment. Non-magnetic gap layer 86 separates pedestal 152from second pole piece 78. Similar to pedestal 152, a back gap pedestal154 is formed on first pole piece layer 80 but in the back gap region. Athird pole piece 156, which is formed in an arcuate fashion with a frontend formed on top of second pole piece 78, serves as a magnetic fluxconnecting layer. Conventional write coils 68 of FIG. 8 are formedwithin the magnetic head in a different manner than that in FIG. 5. Inparticular, a first layer of coil turns are formed below non-magneticgap layer 86 in between pedestals 152 and 154 and a second layer of coilturns are formed above second pole piece 78 within an arcuate spacingformed by third pole piece 156. Other differences from that in FIG. 5are that shield layer 66 and first pole piece layer 80 are not commonlayers; they are separate. A non-magnetic separating layer 150 is formedbetween shield layer 66 and first pole piece layer 80.

FIG. 16 is a flowchart for use in describing a method of making a writecoil of a magnetic head in accordance with the present application. Theflowchart of FIG. 16 is referred to in combination with FIGS. 17–22which are cross-sectional views of partially constructed magnetic headsfor use in describing the steps in the flowchart. The method may be usedto make one or more structures (e.g. a write coil) of the magnetic headin the disk drive described in relation to FIGS. 1–9.

The method begins at a start block 1600 of FIG. 16 and the firstcross-sectional view in FIG. 17. In FIG. 17, a seed layer 1706 made ofruthenium (Ru) is deposited over a substrate (step 1602 of FIG. 16). Thesubstrate may be any suitable substrate and, in FIG. 17, seed layer 1706is formed over an insulator layer 1704 (e.g. Al₂O₃) which is formed overa pole piece layer 1702 (e.g. magnetic materials such as NiFe or CoFe)of a magnetic write head. Seed layer 1706 may be formed with a thicknessof between about 500 and 1500 Angstroms. Preferably, seed layer 1706 ispure ruthenium (Ru); however, other alternatives may be utilized such asosmium (Os).

In FIG. 18, a patterned resist 1802 having a plurality of trenches isformed over seed layer 1706 (step 1604 of FIG. 16). Each trench 1804extends down through patterned resist 1802 until seed layer 1706 isreached; seed layer 1706 is exposed at a bottom of each trench 1804.Each resist separating layer 1806 which separates each trench 1804 fromone another has a pitch P or width as depicted in FIG. 18. In thepresent example, the pitch P or width is 0.5 microns or less. Thethickness or height of each trench 1804 may be between 1 and 15 um.Given these dimensions, the write coil to be formed will be ahigh-aspect ratio structure. In the example shown in FIG. 18, it isillustrated that six (6) trenches 1804 are formed within patternedresist 1802; however more or less trenches may be formed depending onthe application.

Patterned resist 1802 may be a photoresist made of, for example, apolyphenolic polymer or polyvinylphenol. Polyphenolic polymer is acopolymer of phenol and formaldehyde and is also known commercially asNovolak, which can be purchased from Hoechst Celanese, Sumitomo, orShipley. To form patterned resist 1802, a full thin film of resist isinitially formed over seed layer 1706. This thin film of resist islight-exposed in regions which are to be removed, provided the resist isa positive resist. If the resist is a negative resist, it islight-exposed in regions that are to be retained. Next, the resist issubjected to a basic developer solution. The developer used may be, forexample, aqueous potassium hydroxide (KOH) developer, such as 1:6 2401(Shipley) or 1:4 AZ 400 K (Hoechst Celanese) wherein the ratios are thedeveloper-to-water. In a 1:6 2401 developer, the develop time can be upto 3 minutes for the purpose of removing light-exposed resist portions.Other basic aqueous developers may be utilized as well, such as 2.38%tetramethylammonium hydroxide (TMAH).

In FIG. 19, electrically conductive materials 1902 are thenelectroplated within patterned resist 1802 (step 1606 of FIG. 16). Thiselectroplating technique may generally be referred to asthrough-mask-plating (TMP). Using this process, electrically conductivematerials 1902 formed within each trench 1802 make contact with seedlayer 1706 at the bottom of each trench 1802. In this embodiment,electrically conductive materials 1902 are preferably copper (Cu)although any suitable conductive materials may be utilized such as gold(Au), silver (Ag), or alloys thereof. Alternatively, materials 1902 maybe other materials depending on the application; for example, materials1902 may be magnetic materials such as NiFe or CoFe if pole pieces areto be fabricated with use of the present method. In FIG. 20, patternedresist 1802 is removed with use of a suitable solvent (step 1608 of FIG.16) to reveal a plurality of write coil layers 1904. Note that seedlayer 1706 remains intact underneath write coil layers 1904 and isexposed in the side regions as well as in between each write coil layer1904. Each write coil layer 1904 still remains separated by a pitch orwidth as depicted in the drawing.

In FIG. 21, the exposed seed materials are removed with use of areactive ion etch (RIE) in ozone gas (step 1610 of FIG. 16). In this RIEapproach, a plasma is sparked in the ozone gas (O₃) by a radio frequency(RF) source which decomposes to form a species capable of reactingdirectly with the exposed seed layer materials. The reaction producesvolatile compounds, such as RuO₄ and RuO₃, which causes a selectiveremoval of the seed layer materials. The RIE with ozone gas (O₃) isselective to ruthenium and does not etch materials of write coil layer1904. Therefore, the geometry for the write coil does not change (or isinsignificantly changed). Note that outside surfaces of write coil layer1904 may become oxidized to produce a thin oxidized copper layer, butthis poses no significant issues. The RIE is performed until each coillayer 1904 is electrically separated from each adjacent coil layer, andpreferably until all seed layer materials in between each coil layer1904 are removed. A reasonable etch rate of between about 500–3000Angstroms/minute may be achieved using this process. Note that some seedmaterials 2102 that were not exposed remain formed underneath each coillayer 1904.

In FIG. 22, insulator materials 2202 are then deposited in between coillayers 1904 to form a plurality of coil separation layers (step 1612 ofFIG. 16). Insulator materials 2202 may be any suitable non-conductivedielectric materials such as alumina (Al₂O₃) or hard-baked photoresist.A write coil structure 2204 is thereby fabricated. Note that the pitchor width between write coil layers 1904 is depicted as the width of eachnewly formed coil separating layer, as shown in the drawing. After thedeposition of insulator materials 2202, a planarization process such asa chemical-mechanical polishing (CMP) may be subsequently performed toform a top planarized surface over write coil structure 2204. Subsequentprocessing steps, conventional or otherwise, may be utilized to completethe formation of the magnetic head (step 1614 of FIG. 16). For example,additional insulator materials may be deposited to surround and protectthe write coil and additional pole piece components may be formed overthe write coil (e.g. see FIG. 8).

Advantageously, a write coil is fabricated with no damage to its topportion due to etching the seed layer materials. The likelihood ofelectrical shorting the write coil is substantially reduced oreliminated. Note that this technique is not limited to fabrication ofthe write coils and may apply to the fabrication of magnetic pole piececomponents including pole piece layers and pedestals (e.g. see FIGS.6–9), for example. To fabricate a magnetic pedestal, for example, themethod may include the steps of forming a ruthenium (Ru) seed layer overa substrate; forming a patterned resist having a pedestal trench overthe Ru seed layer; electroplating magnetic materials within the pedestaltrench to form the pedestal; removing the patterned resist; andperforming a RIE in ozone gas (O₃) to remove Ru seed layer materialsexposed outside the electroplated pedestal.

Final Comments. Methods suitable for use in making a write coil of amagnetic head have been described. One illustrative embodiment of makinga write coil includes the steps of forming a seed layer made ofruthenium (Ru) over a substrate; forming, over the seed layer, apatterned resist having a plurality of write coil trenches patternedtherein; electroplating electrically conductive materials within theplurality of write coil trenches to thereby form a plurality of writecoil layers; removing the patterned resist; and performing a reactiveion etch (RE) in ozone gas for removing exposed seed layer materials inbetween the plurality of write coil layers. Advantageously, the writecoil layers remain undamaged from the RIE in ozone gas. A more generalmethod for forming an electroplated structure includes the steps offorming a seed layer comprising ruthenium over a substrate; forming,over the seed layer, a patterned resist having one or more trenchespatterned therein; electroplating materials within the one or moretrenches to form one or more electroplated structures; removing thepatterned resist; and performing a RIE in ozone gas for removing exposedseed layer materials.

It is to be understood that the above is merely a description ofpreferred embodiments of the invention and that various changes,alterations, and variations may be made without departing from the truespirit and scope of the invention as set for in the appended claims. Fewif any of the terms or phrases in the specification and claims have beengiven any special particular meaning different from their plain languagemeaning, and therefore the specification is not to be used to defineterms in an unduly narrow sense.

1. A method for use in making a write coil of a magnetic head,comprising: forming a seed layer comprising ruthenium (Ru) over asubstrate; forming, over the seed layer, a patterned resist having aplurality of write coil trenches patterned therein; electroplatingelectrically conductive materials within the plurality of write coiltrenches to thereby form a plurality of write coil layers; removing thepatterned resist; and performing a reactive ion etch (RIE) in ozone gasfor removing exposed seed layer materials in between the plurality ofwrite coil layers.
 2. The method of claim 1, wherein a pitch between thecoil layers is 0.5 microns or less.
 3. The method of claim 1, whereinthe write coil layers remain unetched from the RIE in ozone gas.
 4. Themethod of claim 1, wherein a volatile compound including at least one ofRuO₄ and RuO₃ is produced from the RIE in ozone gas.
 5. The method ofclaim 1, wherein the electrically conductive materials comprise copper(Cu).
 6. The method of claim 1, wherein the seed layer is formed over aninsulator layer.
 7. The method of claim 1, wherein the seed layer isformed over a pole piece layer of the magnetic head.
 8. The method ofclaim 1, further comprising: forming a plurality of insulator layers inbetween the plurality of write coil layers.
 9. The method of claim 1,wherein the seed layer consists of ruthenium (Ru).
 10. A method for usein forming an electroplated structure, comprising: forming a seed layercomprising ruthenium (Ru) over a substrate; forming, over the seedlayer, a patterned resist having one or more trenches patterned therein;electroplating materials within the one or more trenches to form one ormore electroplated structures; removing the patterned resist; andperforming a reactive ion etch (RIE) in ozone gas for removing exposedseed layer materials.
 11. The method of claim 10, wherein a pitchbetween the one or more trenches is 0.5 microns or less.
 12. The methodof claim 10, wherein the one or more electroplated structures remainunetched from the RIE in ozone gas.
 13. The method of claim 10, whereina volatile compound including at least one of RuO₄ and RuO₃ is producedfrom the RIE in ozone gas.
 14. The method of claim 10, wherein theelectroplated materials comprise copper (Cu).
 15. The method of claim10, wherein the electroplated materials comprise magnetic materials. 16.The method of claim 10, wherein the seed layer is formed over aninsulator layer.
 17. The method of claim 10, wherein the seed layer isformed over a pole piece layer of a magnetic head.
 18. The method ofclaim 10, wherein the seed layer consists of ruthenium (Ru).
 19. Amagnetic head having a write coil formed by a method comprising thesteps of: forming a seed layer comprising ruthenium (Ru) over asubstrate; forming, over the seed layer, a patterned resist having aplurality of write coil trenches patterned therein; electroplatingelectrically conductive materials within the plurality of write coiltrenches to thereby form a plurality of write coil layers; removing thepatterned resist; and performing a reactive ion etch (RIE) in ozone gas(O₃) for removing exposed seed layer materials in between the pluralityof write coil layers.
 20. The magnetic head of claim 19, wherein a pitchbetween the coil layers is 0.5 microns or less.
 21. The magnetic head ofclaim 19, wherein the write coil layers remain unetched from the RIE inozone gas.
 22. The magnetic head of claim 19, wherein a volatilecompound including at least one of RuO₄ and RuO₃ is produced from theRIE in ozone gas.
 23. The magnetic head of claim 19, wherein theelectrically conductive materials comprise copper (Cu).
 24. The magnetichead of claim 19, wherein the seed layer is formed over an insulatorlayer.
 25. The magnetic head of claim 19, wherein the seed layer isformed over a pole piece layer of the magnetic head.
 26. The magnetichead of claim 19, further comprising: forming a plurality of insulatorlayers in between the plurality of write coil layers.
 27. The magnetichead of claim 19, wherein the seed layer consists of ruthenium (Ru).